Refining mineral oils



APril 25, 1944 A. J. sHMlDL REFINING MINERAL oILs Filed April 11. 1940 LIIIA .v r

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Patented Apr. 25, 1944 TENT OFFICE REFrNrNG MINERAL ons Albert J. Shmdl, Houston, Tex., assignor to tandard Oil Development Company, a corporation of Delaware Application April 11, 1940, Serial No. 329,014

(Cl. 13S-32) 6 Claims.

lIhe present invention relates to the refining of mineral oils. The invention is particularly concerned with a process for the production of refined high quality petroleum oils, and especially relates to the production of refined high quality petroleum oils boiling in the heating oil, kerosene, and light gas oil boiling ranges, In accordance with the present invention, Detroleum oils, particularly oils boiling in the heating oil boiling range, are processed in an operation comprising a two-stage alkali metal hydroxide treating operation in a manner to substantially completely remove organic acidic bodies having emulsifying properties and then are further treated in a final stage in a manner to remove objectionable sulfur compounds.

A particular adaptation of the present invention comprises a process for the treatment of feed oils to produce petroleum oil products boiling in the motor fuel boiling range and petroleum oil products boiling in the heating oil boiling range in a, manner that undesirable constituents are removed from the products boiling in the heating oil boiling range and incorporated as desirable constituents in the petroleum oils boiling in the motor fuel boiling range whereby heating oil products of improved burning properties and motor fuels having increased stabilities are produced. The present application is a continuation and contains subject matter in common with that-contained in U. S. application Ser. No. 170,598, led October 28, 1937, in the name of Shmidl et al.

It is Well known in the art to rene petroleum oils by various distilling, cracking, reforming, and related operations. It is also well known to produce refined oil fractions boiling in the kerosene, heating oil, and light gas oil boiling ranges from various distilling and cracking operations. These refined oil fractions, particularly those segregated in the craclcing of various gas oils and reduced crudes, generally contain objectionable sulfur compounds which must be removed by a further refining treatment. One method generally employed is to contact the heating oil fractions with a so-called doctor solution which essentially comprises an aqueous solution of `sodium hydroxide containing dissolved therein sodium plumbite. This treatment removes the hydrogen sulfide and converts the undesirable mercaptan compounds to corresponding innocuous disuldes. This treatment, however, has not been entirely satisfactory due to the fact that emulsions form which are difficult to break. This is particularly the case when the heating lll oil fractions contain naturally occurring organic acids and acidic compounds, as for example, phenolic type constituents, alkylated hydroxyl aryl materials and other compounds having an indenite acidic nature of an alkylated cyclic structure. In order to remove these materials which function as emulsifying agents it has been suggested that the oil :prior to treating the same for the removal of mercaptans and the like be pretreated. One method employed is to pretreat the oil With an aqueous alkali metal hydroxide solution, as for example, an aqueous sodium hydroxide solution. While this method serves to remove a portion of the materials hereinbefore referred to which are regenerated and employed as valuable addition agents for inhibiting lower boiling petroleum fractions, the process is not satisfactory for conditioning the oil so that an efficient operation is secured in the removal of the mercaptans. A particular disadvantage of a single stage alkali metal hydroxide treating system is that it is practically impossible to substantially completely remove these materials from the oil even when using a considerable excess of the alkali metal hydroxide treating solution. I have now discovered a process by which it is possible to produce a high quality petroleum oil fraction boiling in the heating oil, kerosene, and light gas oil boiling range Which comprises a two-stage alkali metal hydroxide treating system and a stage in which undesirable mercaptans are efficiently and economically removed, preferably by means of a doctor treating operation. A particularly desirable modification of my invention comprises an operation in which the undesirable emulsifying agents are substantially completely removed from the petroleum oil boiling in the heating oil, kerosene, and light gas oil boiling range in a manner to secure a substantially improved doctor sweetening operation and in a manner in which the removed emulsifying agents are incorporated as desirable addition agents in a lower boiling fraction, preferably a fraction boil- F ing within the motor fuel boiling fraction, to render the same stable against deterioration resulting in the formation of gum and hard carbon.

l The process of my invention may be readily understood by reference to the attached drawing illustrating modifications of the same. For the purposes of illustration it is assumed that a heating oil fraction boiling in the range from about 400 F. to 600 F. is produced from a feed petroleum oil boiling in the gas oil range of from about 400 F. to '700 F. The feed oil is introduced into cracking equipment 2 by means of feed line I in which it is subjected to temperature and pressure conditions for an optimum time period adapted to produce a petroleum oil fraction boiling in the motor fuel boiling range and said petroleum oil fraction boiling in the heating oil boiling range of from about 400 F. to 600 F. The segregated petroleum oil fraction boiling in the motor fuel boiling range is removed from cracking equipment 2 by means of line 3, acid treated in acid treating unit 4, and passed to neutralization unit by means of line '6. Acid is introduced into acid treating unit 4 by means of line 1 and withdrawn by means of line 8. The acid oil is neutralized in neutralization unit 5 by means of an alkali metal hydroxide solution which is introduced by means of line 9 and withdrawn by means of line Ill. The neutralized oil is withdrawn from neutralization unit 5 by means of line II and introduced into distillation unit I2 from which a petroleum oil product of the desired end point is removed overhead by means of line I3, sweetened in sweetening unit I4 preferably by means of a caustic solution and passed to storage or otherwise utilized by means of line I5. Generally, it is preferred to sweeten the neutralized oil removed from unit 5 in sweetening unit IG which preferably comprises a doctor sweetening operation. The bottoms from distillation unit I2 are Withdrawn by means of line I1 and disposed of in any manner desirable.

The heating oil fraction derived from the gas oil and segregated in cracking unit 2 is Withdrawn by means of line I8 and introduced into initial stage I9 of an alkali metal hydroxide solution treating system. For purposes of illustration, it is assumed that the alkali metal hydroxide solution comprises an aqueous solution of sodium hydroxide. Prior to introducing the heating oil into initial stage I 9 it is mixed with a spent sodium hydroxide solution Withdrawn from the secondary stage 2e which is introduced by means of line 3l. In order to secure adequate mixing the heating oil and the spent sodium hydroxide are passed through mixer 22 prior to introducing the mixture into initial stage I9. Temperature and pressure conditions are adjusted in initial stage I3 to remove as a bottoms by means of line 23 a soap solution comprising complex salts and sodium salts of phenolic acids and naphthenic acids. The partially treated oil is Withdrawn from initial stage I9 by means of line 24, mixed with fresh sodium hydroxide solution which is introduced by means of line 25, passed through mixer 26, and introduced into secondary stage 20 by means of line 21. Temperature and pressure conditions are adjusted in secondary stage 20 so as to remove by means of line 28 a treated heating oil fraction substantially free of phenolic type and naphthenic type constituents and other constituents having emulsifying tendencies, and to remove by means of line 219 preferably a twophase mixture comprising a sodium hydroxide under conditions adapted to dissolve an amount of free sulfur. The sulfur oil is Withdrawn from sulfur tower 33 by means of line 34 and intro duced into mixer 35 in which it -contacts the remainder of the treated oil and the doctor reagent comprising a sodium hydroxide solution of lead plumbite which is introduced by means of line 38. The mixture is withdrawn from mixer 35 and passed to doctor settler 31 by means oi line 38. The spent doctor is Withdrawn from settler 31 by means of line 39 While the treated heating oil product is withdrawn by means of line 40, passed to storage and handled in any manner desirable. Under certain conditions, it may be preferred to Water-wash the treated oil withdrawn from the settler, in Which case the oil is passed through water-Washing unit 4I by means of line 42. The Water-Washed oil is Withdrawn from water-Washing unit 4I by means of line 43 and passed to storage in the manner described.

The salt solution removed from the initial stage I9 of the sodium hydroxide treating plant is introduced into regeneration unit 44 and contacted With the Weak acid solution, such as sul furie acid or a hydrochloric acid solution, carbon dioxide, or gases containing carbon dioxide, to convert the salts into the original acidic compounds. The acidifying agent is introduced into unit 44 by means of line 45 and Withdrawn by means of line 40. The regenerated naturally occurring organic acids are withdrawn from acid ifying unit 44 by means of line 41 and handled in any manner desirable. In general, it is preferred to pass the crude acids by means of line 48 into distillation unit 49 and to remove as an overhead product by means of line 50 approximately 80% of the crude organic acids. The bottoms are withdrawn by means of line 5I and handled in any manner desirable. These crude acids Withdrawn by means of line 50 may be passed to storage by means of line 51, but are preferably incor-v porated in the low boiling motor fuel which is passed to storage by means of line I5.

A particularly desirable adaptation of the present invention is to remove the salt solution from initial settler I9 by means of line 52 and to incorporate this solution with the acid oil removed from acid treating unit 4 by means of line 53. Under certain conditions, this solution may be introduced into distillation unit l2 by means of line 54. By operating in this manner, the acid constituents of the lower boiling oil may be neu tralized, resulting in the regeneration of the salts to form the corresponding organic acids,

which materials function as inhibiting agents in the nished treated product.

The process of the present invention may be widely varied. Although it may be employed in the treatment of any petroleum oil which is to be subjected to a treatment adapted to remove mercaptan compounds, particularly by doctor sweetening the same, it is especially applicable for the production of rened oils of improved quality boiling in the kerosene, heating oil, and light gas oil boiling ranges. Particularly desirable oils are heating oil fractions boiling in the range from about 400 F. to 600 F. In accordance with the present invention it is essential that the petroleum oil prior to doctor sweetening the same be contacted in a two-stage alkali metal hydroxide solution operation. It is essential that the fresh alkali metal hydroxide solution be introduced into the secondary stage with the partially treated oil withdrawn from the initial stage f and that the spent alkali metal hydroxide solution comprising a substantial concentration of salts be introduced with the fresh feed to the initial treating stage. In general, it is preferred to employ an aqueous solution of sodium hydroxide in a manner that two distinct phases form in the secondary treating stage comprising a sodium hydroxide phase and a phase having a relatively high concentration of sodium salts of the acidic materials.

The quantity of alkali metal hydroxide solution employed may vary widely and will be a function of the particular alkali metal hydroxide solution utilized, as well as the character of the oil being treated. For example, when employing a sodium hydroxide solution, the concentration should be in the range from about 25 to 50 B. In general, the concentration should not exceed about 40 B and a particularly desirable concentration is in the range from 30 to 35 B. In general, a sufficient quantityis employed to completely theoretically neutralize acidic constituents present in the feed oil. Thus, when using solutions of the concentration enumerated, from about 0.1 pound to 0.25 pound of sodium hydroxide solution is employed per barrel of oil being treated. It has been found that satisfactory results are secured when employing a 40 B. solution in an amount of about 0.15 pound of sodium hydroxide per barrel of oil being treated.

The temperatures and pressures employed in the alkali metal hydroxide treating system are preferably atmospheric although, if desired, elevated temperatures and pressures may be utilized. The salts removed from the initial stage are preferably regenerated by acidication with carbon dioxide since no control is necessary to avoid an excess and since the acidified products contain less water than when using dilute mineral acids. Moreover, the use of a weak acidied agent such as carbon dioxide permits selective acidification of the salts. Furthermore, the use of carbon dioxide avoids a formation of polymer product which may result from the use of mineral acids. 'I'he extract appears to be composed largely of alkylated hydroxyl aryl compounds and other compounds of more indefinite acidic nature having an alkylated cyclic structure. These compounds have been found to have particular value as addition agents for inhibiting the formation of gum and motor fuel. To this end they may be added to the motor fuel in amounts varying from 0.1% to 1.0% of the extracted material. It has been found that this material has a stabilizing effect on the motor fuel, retarding the formation of objectionable gums. This extract has been found particularly effective as an inhibitor when the concentration of the alkaline solution is regulated within the processed limits hereinbefore pointed out. When weaker solutions are employed, the extracted product does not have the same benecial properties. If stronger solutions are employed, difficulty is encountered in effecting the separation due to the emulsication of the oil and the caustic solution. While the crude extract may be employed as a gum inhibitor in motor fuels, it is preferred to further purify the product by vacuum distillation at a temperature of about 400 removing about 80% as overhead products and discarding the nal 20%. This distillation has been found to materially reduce the sulfur content. The extract likewise may be employed as a resin base or as a wood preservative.

It has also been found that the quality of kerosene, furnace oils, and other similar burning oils is materially improved by the alkaline treatment followed by a treatment adapted to removev undesirable sulfur compounds in the manner described. The oil so treated has better burning properties in that it burns with a clearer flame, With less smoke, and is of a better color and considerably more stable than the original untreated oil.

A particular adaptation of the present invention is to utilize the salt solution for neutralizing a lower boiling oil, preferably an oil boiling in the motor fuel boiling range which has been contacted with acid in order to completely neutralize the same and to release desirable inhibiting substances therein. Thus, the invention may be readily employed in the production of a motor -fuel having improved stability characteristics and a heating oil of improved burning characteristics from a feed oil by removing undesirable constituents from said heating oil and incorporating the same in the motor fuel in the manner described.

In order to further illustrate the invention, the following example is given which should not be construed as limiting the same in any manner whatsoever:

Example In an operation for the production of heating oils it Was found that undesirable sulfur compounds could not be readily removed by contacting the same with a doctor solution due to extensive emulsication dimculties. In order to overcome these emulsification difliculties the oil, prior to doctor sweetening, was contacted in a single stage treater employing 0.15 pound of 40 B. sodium hydroxide solution per barrel of oil charge to the doctor sweetening plant which was substantially the theoretical amount of sodium hydroxide necessary to completely neutralize the naturally occurring organic acidic constituents. This pretreatment did not suiciently reduce the emulsication difficulties incurred in the doctor sweetening operation and it was found that only about 50% of the acidic constituents were removed from the oil. In another operation the sodium hydroxide solution was intimately mixed with the oil in a batch turbo mixer and it was found that only about 75% of the acid oil constituents were removed.

However, in an operation conducted in the manner described in accordance with the present invention employing a two-stage treatment it was found that approximately of the naturally occurring acidic substances were removed when the oil was treated with 0.15 pound of 40 B. caustic which was substantially the theoretical amount necessary to completely neutralize said constituents.

The process of the present invention is not to be limited by any theory or mode of operation, but only in and by the following claims in which it is desired to claim all novelty in so far as the prior art permits.

I claim:

l. Process for the production of rened petroleum oil products of improved burning properties boiling in the kerosene, furnace oil, and light gas oil boiling ranges containing substantial quantities of emulsifying agents which comprises contacting the feed oil in a two-stage alkali metal hydroxide treating system in a manner in which the oil in the initial stage is contacted with the entire amount of the spent metal hydroxide solution removed from the secondary stage and in which the oil withdrawn from said initial stage is contacted solely with fresh alkali metal hydroxide solution in said secondary stage, removing the treated oil from said secondary stage substantially completely free of emulsifying agents and treating the same in a tertiary stage with a doctor solution to remove objectionable sulfur compounds therefrom.

2. Process in accordance With claim 1 in which said feed oil boils in the range from about 400 F. to 600 F., in which said alkali metal hydroxide solution is a sodium hydroxide solution.

3. Process in accordance with claim 1 in which said feed oil boils in the range from about 400 F. to 600 F. and in Which said feed oil is contacted in said two-stage alkali metal hydroxide treating system with from about 0.1 pound to .25 pound of 30 to 50 B. sodium hydroxide solution per barrel of oil treated.

4. Process for the production of a refined petroleum oil product boiling in the motor fuel boiling range of increased stability and for the production of a petroleum oil product boiling in the heating oil boiling range of improved burning properties from a petroleum feed oil boiling in the gas oil boiling range comprising subjecting the feed gas oil to temperature and pressure conditions for the desired time period adapted to produce a petroleum oil product boiling in the motor fuel boiling range and a petroleum oil product boiling in the heating oil boiling range, contacting the product boiling in the heating oil boiling range in a two-stage alkali metal treating systemin a manner in which the oil in the initial stage is contacted solely with the entire amount of the spent alkali metal hydroxide solution removed from the secondary stage and in which the oil Withdrawn from said initial stage is contacted solely With fresh alkali metal hydroxide solution in said secondary stage, removing the treated oil from said secondary stage substantially completely free of emulsifying agents and treating the same in a tertiary stage with a doctor solution to remove objectionable sulfur compounds therefrom, acid treating said product boiling in the'motor fuel boiling range, separating the acid sludge from the resulting acid oil, separating the alkali metal hydroxide eX- tract from the treated oil in said initial stage, and combining the same with the acid treated oil.

5. Process in accordance with claim 4 in which the petroleum oil product boiling in the heating oil boiling range boils in the range from about 400 F. to 600 F., in which said alkali metal hydroxide solution is a sodium hydroxide solution.

6. Process in accordance with claim 4 in which the petroleum oil product boiling in the heating oil boiling range boils in the range from about 400 F. to 600 F. and in Which said heating oil product is contacted in said two-stage alkali metal hydroxide treating system with from about 0.1 pound to .25 pound of 30 to 50 B. sodium hydroxide solution per barrel of oil treated.v

` ALBERT J. SHMIDL. 

